Metal-oxide-semiconductor field effect transistors (MOSFET) are the workhorse of the silicon (Si) semiconductor industry. The rapid advance of portable electronic systems and the exponential increase in integration density has spurred the transition to low-power technologies. Reduction of the supply voltage is key for reducing power dissipation. At the present time, Si CMOS offers significant advantages in terms of integration level and cost; however, reductions in circuit speed of scaled Si CMOS (including SOI) are anticipated as the power supply is reduced to 1 V or below. In contrast to Si, complementary GaAs exhibits optimum speed/power performance and efficiency at a low supply voltage of 1 V and below.
For compound semiconductors, prior art comprises the use of a metal-semiconductor junction as a gate electrode in field effect transistors instead of the standard metal-oxide-semiconductor junction employed in Si technology. The use of a metal semiconductor junction, however, results in excessive leakage current, high power dissipation, reduced logic swing, reduced design flexibility, and limited device performance. Consequently, optimum device performance and high IC integration levels could not be realized and commercial marketability has been limited.
Thus what is needed are new and improved compound semiconductor devices and methods of fabrication which overcome these problems. What is also needed are new and improved compound semiconductor field effect transistors (FET). What is also needed are new and improved compound semiconductor FETs using metal-oxide-semiconductor junctions (MOSFET). What is also needed are new and improved compound semiconductor MOSFETs using a self-aligned gate structure. What is also needed are new and improved self-aligned compound semiconductor MOSFETs using enhancement mode operation. What is also needed are new and improved self-aligned compound semiconductor MOSFETs with stable and reliable device operation. What is also needed are new and improved self-aligned compound semiconductor MOSFETs which enable optimum compound semiconductor device performance. What is also needed are new and improved self-aligned compound semiconductor MOSFETs with optimum efficiency and output power for RF and microwave applications. What is also needed are new and improved self-aligned compound semiconductor MOSFETs for use in complementary circuits and architectures. What is also needed are new and improved self-aligned compound semiconductor MOSFETs for low power/high performance complementary circuits and architectures. What is also needed are new and improved self-aligned compound semiconductor MOSFETs which offer the design flexibility of complementary architectures. What is also needed are new and improved self-aligned compound semiconductor MOSFETs which keep interconnection delays in ULSI under control.
What is also needed are new and improved methods of fabrication of self-aligned compound semiconductor MOSFETs. What is also needed is new and improved methods of fabrication of self-aligned compound semiconductor MOSFETs which are compatible with established complementary GaAs heterostructure FETs (CGaAs) technologies. What is also needed are new and improved compound semiconductor MOSFETs which are relatively easy to fabricate and use.